1. Field of the Invention
The present invention relates to a process for the production of styrene.
More specifically, the present invention relates to a process for the production of styrene starting from benzene and ethane.
Even more specifically, the present invention relates to a process for the production of styrene by the simultaneous dehydrogenation of ethylbenzene and ethane to give styrene and ethylene respectively.
2. Description of the Background
As is well known, styrene is a product which is used in the production of thermoplastic polymers, such as polystyrenes (PS), acrylonitrile-butadiene-styrene copolymers (ABS), styrene-acrylonitrile resins (SAN), styrene-butadiene elastomeric copolymers (SBR) and in formulations for unsaturated polyester resins.
Styrene is generally prepared by the adiabatic or isothermic catalytic dehydrogenation of ethylbenzene in the presence of catalysts selected from metal oxides or their mixtures. In published international patent application W097-18034, for example, the catalyst consists of a mixture comprising Fe.sub.2 O.sub.3, K.sub.2 O, MnO.sub.3, MgO, at least one oxide of Cu, Zn, Sc, Ti, W, Mn, Ni, Pd, Al, P, Bi, B, Sn, Pb and Si and at least two rare-earth metals. In Italian patent application MI97A-1463, on the other hand, the catalyst consists of a mixture of Cr.sub.2 O.sub.3, SnO and at least one alkaline oxide supported on alumina in delta or theta phase. Further information on the dehydrogenation of ethylbenzene is available in Stanford Research Institute (SRI International) Report 338, 1977.
Ethylbenzene is, in turn, prepared by the alkylation of benzene, available as a refinery product, with ethylene coming from the cracking or dehydrogenation of ethane. The alkylation reaction can be carried out in vapour phase, using as catalysts zeolites with high SiO.sub.2 /Al.sub.2 O.sub.3 ratios, for example zeolites of the type ZSM-5 or Lewis acids, or in liquid phase. Details on the alkylation of benzene with ethylene are available in SRI.
The tradional methods for the production of styrene therefore generally require the availability of ethylene for the preparation of ethylbenzene.